Relevant report: After finally pulling some of the American tins from deep in the cellar I transferred several to jars thanks to a wake-up call here... SNIP
A little more to report for your consideration: I accidentially opened a couple 25+ year old tins in perfect condition, so even though food saver bags lost their seal, they kept most rust at bay, which might be important to you in a similar situation.
After so many years, from what I understand, the aging benefits are miniscule in perfect tins. The tobacco has changed for the better in these, but I didn't hear angels sing or anything that profound.
So, my experience here is with vac-bagged unopened tins. Without signs of rust, so I don't pop another good tin, I'm re-bagging the tins because it is really cool to pop a fresh tin from the last century, and mold has not been a problem at all. Also, you might as well just leave tins that have lost their seal, sealed and bag them for a little continued rust "resistance" until rust is evident. They're dry anyway already.
I can't say whether jarring a perfect tin's contents continues the aging process.
Anything with a hint of rust is getting jarred, because the rust sometimes clings to the tobacco. I'm in doubt, though, because a lot of the tins were aluminum (I think) and the "rust" must be tobacco moisture because aluminum rust isn't tobacco colored, right? Maybe I should have pried it off the walls but I didn't.